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[GlobalISel] Don't translate br to layout successor.

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MI can represent fallthrough to layout successor blocks, and our
post-isel representation uses that extensively.

We might as well use it too, to avoid translating and carrying along
unnecessary branches.

llvm-svn: 298459
This commit is contained in:
Ahmed Bougacha 2017-03-21 23:42:50 +00:00
parent c8470e59bc
commit e8e1fa3a7c
2 changed files with 34 additions and 10 deletions
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7
llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
View File

@ -223,10 +223,13 @@ bool IRTranslator::translateBr(const User &U, MachineIRBuilder &MIRBuilder) {
const BasicBlock &BrTgt = *cast<BasicBlock>(BrInst.getSuccessor(Succ));
MachineBasicBlock &TgtBB = getMBB(BrTgt);
MIRBuilder.buildBr(TgtBB);
MachineBasicBlock &CurBB = MIRBuilder.getMBB();
// If the unconditional target is the layout successor, fallthrough.
if (!CurBB.isLayoutSuccessor(&TgtBB))
MIRBuilder.buildBr(TgtBB);
// Link successors.
MachineBasicBlock &CurBB = MIRBuilder.getMBB();
for (const BasicBlock *Succ : BrInst.successors())
CurBB.addSuccessor(&getMBB(*Succ));
return true;

37
llvm/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
View File

@ -52,18 +52,40 @@ define void @allocai64() {
; CHECK: body:
;
; ABI/constant lowering and IR-level entry basic block.
; CHECK: {{bb.[0-9]+}} (%ir-block.{{[0-9]+}}):
; CHECK: {{bb.[0-9]+}}.entry:
;
; Make sure we have one successor and only one.
; CHECK-NEXT: successors: %[[END:bb.[0-9]+.end]](0x80000000)
; CHECK-NEXT: successors: %[[BB2:bb.[0-9]+.bb2]](0x80000000)
;
; Check that we emit the correct branch.
; CHECK: G_BR %[[END]]
; CHECK: G_BR %[[BB2]]
;
; Check that end contains the return instruction.
; CHECK: [[END:bb.[0-9]+.end]]:
; CHECK-NEXT: RET_ReallyLR
;
; CHECK: {{bb.[0-9]+}}.bb2:
; CHECK-NEXT: successors: %[[END]](0x80000000)
; CHECK: G_BR %[[END]]
define void @uncondbr() {
entry:
br label %bb2
end:
ret void
bb2:
br label %end
}
; CHECK-LABEL: name: uncondbr_fallthrough
; CHECK: body:
; CHECK: {{bb.[0-9]+}}.entry:
; CHECK-NEXT: successors: %[[END:bb.[0-9]+.end]](0x80000000)
; We don't emit a branch here, as we can fallthrough to the successor.
; CHECK-NOT: G_BR
; CHECK: [[END]]:
; CHECK-NEXT: RET_ReallyLR
define void @uncondbr() {
define void @uncondbr_fallthrough() {
entry:
br label %end
end:
ret void
@ -140,7 +162,6 @@ false:
; CHECK: [[BB_CASE200]]:
; CHECK-NEXT: successors: %[[BB_RET]](0x80000000)
; CHECK: %[[regretc200:[0-9]+]](s32) = G_ADD %0, %[[reg2]]
; CHECK: G_BR %[[BB_RET]]
;
; CHECK: [[BB_RET]]:
; CHECK-NEXT: %[[regret:[0-9]+]](s32) = PHI %[[regretdefault]](s32), %[[BB_DEFAULT]], %[[regretc100]](s32), %[[BB_CASE100]]
@ -232,7 +253,7 @@ phi.block:
; CHECK: {{bb.[0-9]+.entry}}:
; Make sure we have one successor
; CHECK-NEXT: successors: %[[BB_L1:bb.[0-9]+.L1]](0x80000000)
; CHECK: G_BR %[[BB_L1]]
; CHECK-NOT: G_BR
;
; Check basic block L1 has 2 successors: BBL1 and BBL2
; CHECK: [[BB_L1]] (address-taken):
@ -525,8 +546,8 @@ define void @unreachable(i32 %a) {
; CHECK-LABEL: name: constant_int
; CHECK: [[IN:%[0-9]+]](s32) = COPY %w0
; CHECK: [[ONE:%[0-9]+]](s32) = G_CONSTANT i32 1
; CHECK: G_BR
; CHECK: {{bb.[0-9]+}}.next:
; CHECK: [[SUM1:%[0-9]+]](s32) = G_ADD [[IN]], [[ONE]]
; CHECK: [[SUM2:%[0-9]+]](s32) = G_ADD [[IN]], [[ONE]]
; CHECK: [[RES:%[0-9]+]](s32) = G_ADD [[SUM1]], [[SUM2]]
@ -1181,7 +1202,7 @@ define i8* @test_const_placement() {
; CHECK: bb.{{[0-9]+}} (%ir-block.{{[0-9]+}}):
; CHECK: [[VAL_INT:%[0-9]+]](s32) = G_CONSTANT i32 42
; CHECK: [[VAL:%[0-9]+]](p0) = G_INTTOPTR [[VAL_INT]](s32)
; CHECK: G_BR
; CHECK: {{bb.[0-9]+}}.next:
br label %next
next: